Semiconductor device and method of its manufacture

ABSTRACT

The present invention presents a semiconductor device ( 10 ) which is adapted to a solar cell, and in which a semiconductor element ( 1 ) is produced by forming one flat surface ( 2 ) on a spherical or substantially spherical silicon single crystal ( 1   a,    1   b ). A diffusion layer ( 3 ) and a substantially spherical pn junction ( 4 ) are formed on this semiconductor element ( 1 ), and a diffusion-mask thin film ( 5 ) and a positive electrode ( 6   a ) are formed on the flat surface ( 2 ). A negative electrode  6   b  is formed at the apex on the opposite side to the positive electrode ( 6   a ), and an antireflection film ( 7 ) is formed on the surface side of the diffusion layer ( 3 ).

TECHNICAL FIELD

The present invention relates to a semiconductor device with a lightemitting or light receiving function that incorporates a plurality ofsubstantially spherical semiconductor devices, and to the making methodthereof. This semiconductor device can be applied to a variety ofapplications such as a solar cell panel, a lighting panel, a display,and a semiconductor photocatalyst.

BACKGROUND ART

Conventionally, research has been directed toward a technology thatinvolves forming a pn junction, via a diffusion layer, on a surface of asmall-diameter spherical semiconductor element made of a p-type orn-type semiconductor and then connecting a plurality of these sphericalsemiconductor elements in parallel to a common electrode, thistechnology being put to practical use for solar cells, semiconductorphotocatalysts, and so forth.

U.S. Pat. No. 3,998,659 discloses an example in which a solar cell isconstituted by forming a p-type diffusion layer on the surface of an-type spherical semiconductor, connecting the respective diffusionlayers of a plurality of spherical semiconductors to a common film-likeelectrode (positive electrode), and then connecting the n-type coresections of these spherical semiconductors to a common film-likeelectrode (negative electrode).

U.S. Pat. No. 4,021,323 discloses a solar energy converter(semiconductor module) having the following constitution. Plural p-typespherical semiconductor elements and plural n-type sphericalsemiconductor elements are placed in series, and connected to a commonfilm-like electrode, and respective diffusion layers of thesesemiconductor elements are made into contact with a common electrolyticsolution, and then by irradiating with solar light, electrolysis of theelectrolytic solution is induced.

So too in the case of the modules having spherical cells appearing inU.S. Pat. Nos. 4,582,588 and 5,469,020, because the spherical cells areattached by being connected to a sheet-like common electrode, aplurality of spherical cells are suitable for connecting in parallel.However, they are not suitable for serial connection.

On the other hand, as shown in International Patent Publication Nos.WO98/15983 and WO99/10935, the inventor of the present invention hasproposed a granular light emitting or light receiving semiconductordevice in which a diffusion layer, pn junction, and a pair of electrodesare formed on a spherical semiconductor element made of a p-typesemiconductor or an n-type semiconductor. Also, proposed is asemiconductor module, which is produced by connecting a plurality of thesemiconductor device in series and then connecting a plurality of theserially connected bodies in parallel, and which can be applied to asolar cell, a photocatalyst device for electrolysis of water and soforth, a variety of light emitting devices, and color displays, and thelike.

In the case of this semiconductor module, when any semiconductor deviceof any serially connected body enters an open state due to failure,current no longer flows to the serial circuit including above failedsemiconductor element, and the remaining normal semiconductor devices inthe serially connected body also enter a breakdown state, wherebydropping of the output of the semiconductor module is generated.

In addition, in the case of the spherical semiconductor devices havingthe positive and negative electrodes that were proposed by the presentinventor, handling is a problem because the device is prone to rolling,and it is not easy to determine the position for forming the positiveand negative electrodes nor to distinguish the positive and negativeelectrodes during assembly.

Therefore, the inventor of this application undertook research withrespect to a technology for forming a pair of flat surfaces on aspherical semiconductor element and then for forming electrodes on theseflat surfaces. However, not only was there then a large number ofprocesses for the electrode formation, it also became evident that itwas still not easy to distinguish between the positive and negativeelectrodes and that this technology was not very advantageous in termsof mass producing the semiconductor module by using a multiplicity ofspherical semiconductor devices.

An object of the present invention is accordingly to provide asubstantially spherical semiconductor device having one flat surface, isnot prone to rolling and can be handled easily. Another object of thepresent invention is to provide a semiconductor device in which a firstelectrode is formed on the flat surface and a second electrode is formedat the apex on the opposite side to this electrode such that the centerof the semiconductor device is interposed between the first and secondelectrodes, and in which the positive and negative electrodes can beeasily distinguished. A further object of the present invention is toprovide a making method for this semiconductor device.

DISCLOSURE OF THE INVENTION

The semiconductor device according to the present invention comprises: asemiconductor element, which has a flat surface formed by removing anapex part of a substantially spherical semiconductor crystal made of ap-type or n-type semiconductor; a diffusion layer or semiconductorthin-film deposition layer formed on the surface of the semiconductorelement excluding the flat surface and a substantially spherical pnjunction formed via the diffusion layer or semiconductor thin-filmdeposition layer; and first and second electrodes, which are provided onthe flat surface and at the apex on the opposite side to the flatsurface respectively so as to face each other with the center of thesemiconductor element interposed therebetween, and which are connectedto both ends of the pn junction.

Further, a semiconductor device making method according to the presentinvention comprises: a first step of making a substantially sphericalsemiconductor crystal made of a p-type or n-type semiconductor; a secondstep of producing a semiconductor element which has a flat surfaceformed by removing an apex part of the semiconductor crystal; a thirdstep of forming a diffusion layer or semiconductor thin-film depositionlayer on the surface of the semiconductor element excluding the flatsurface and forming a substantially spherical pn junction via thediffusion layer or semiconductor thin-film deposition layer; and afourth step of forming first and second electrodes, which are connectedto the two ends of the pn junction, on the flat surface and at the apexon the opposite side to the flat surface respectively so that theseelectrodes face each other with the center of the semiconductor elementinterposed therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 38 show embodiments of the present invention.

FIGS. 1(a) and 1(b) are cross-sectional views of a sphericalsemiconductor crystal and a substantially spherical semiconductorcrystal respectively;

FIG. 2 is a cross-sectional view of a semiconductor element having aflat surface;

FIG. 3 is a cross-sectional view of a semiconductor element having adiffusion-mask thin film;

FIG. 4 is a cross-sectional view of the semiconductor element in FIG. 3,an acid-resistant sheet and an acid-resistant wax;

FIG. 5 is a cross-sectional view of a semiconductor element on which apartial diffusion-mask thin film remains;

FIG. 6 is a cross-sectional view of a semiconductor element having adiffusion layer, a pn junction and an antireflection film;

FIG. 7 is a cross-sectional view of a semiconductor element with pastingan electrode-forming aluminum paste and silver paste to thesemiconductor element of FIG. 6;

FIG. 8 is a cross-sectional view of a semiconductor element having apair of electrodes formed by heat-treating the semiconductor element ofFIG. 7.

FIG. 9 is a plan view of a lead frame;

FIG. 10 is a cross-sectional view of the lowest lead frame and paste;

FIG. 11 is a cross-sectional view of an intermediate lead frame andpaste;

FIG. 12 is a plan view of an assembly body produced by integrating aplurality of semiconductor devices and a plurality of lead frames;

FIG. 13 is a front view of the assembly body;

FIG. 14 is a plan view of a lead frame, and three sets of semiconductormodules molded with a light transmitting member made of a transparentsynthetic resin;

FIG. 15 is a cross-sectional view along the line XV-XV in FIG. 14;

FIG. 16 is a plan view of a semiconductor module;

FIG. 17 is a front view of a semiconductor module; and

FIG. 18 is an equivalent circuit of the semiconductor module.

FIG. 19 is a plan view of a lead frame and a one-set semiconductormodule molded with a light transmitting member made of a transparentsynthetic resin, relating to a second modified embodiment;

FIG. 20 is a cross-sectional view along the line XX-XX in FIG. 19;

FIG. 21 is a plan view of a semiconductor module relating to a thirdmodified embodiment; and

FIG. 22 is a cross-sectional view along the line XXII-XXII in FIG. 21.

FIG. 23 is a plan view of a base sheet relating to a fourth modifiedembodiment;

FIG. 24 is a plan view of the base sheet with connecting leads;

FIG. 25 is a plan view of a base sheet on which the semiconductordevices are mounted;

FIG. 26 shows an end face view of an assembly body produced byassembling the base sheet and semiconductor devices;

FIG. 27 shows an end face view of a semiconductor module comprising thebase sheet, semiconductor devices and a light transmitting member;

FIG. 28 shows the end face view of the semiconductor module in which thesemiconductor module in FIG. 27 is partially modified;

FIG. 29 is a plan view of a base sheet different from the one mentionedabove; and

FIG. 30 is a vertical cross-sectional view of the base sheet in FIG. 29.

FIG. 31 is a cross-sectional view of a semiconductor element relating toa fifth modified embodiment;

FIG. 32 is a cross-sectional view of a semiconductor element having asilicon growth layer and a pn junction on the semiconductor element inFIG. 31;

FIG. 33 is a cross-sectional view of a semiconductor element having anantireflection film on the semiconductor element in FIG. 32; and

FIG. 34 is a cross-sectional view of a semiconductor device havingpositive and negative electrodes on the semiconductor element in FIG.33.

FIG. 35 is a cross-sectional view of a semiconductor element relating toa sixth modified embodiment;

FIG. 36 is a cross-sectional view of a semiconductor element having ap-type base layer on the semiconductor element in FIG. 35;

FIG. 37 is a cross-sectional view of a semiconductor element having ann-type emitter layer on the semiconductor element in FIG. 36; and

FIG. 38 is a cross-sectional view of an npn phototransistor.

MOST PREFERRED EMBODIMENT OF THE INVENTION

Embodiments of the present invention will be described hereinbelow onthe basis of the drawings. First of all, the semiconductor device willbe described as a solar cell that is incorporated into a semiconductormodule.

FIGS. 1 to 8 show a making method of a light receiving semiconductordevice 10 as a solar cell. FIG. 8 is a cross-sectional view of afinished light receiving semiconductor device 10.

As shown in FIG. 8, the light receiving semiconductor device 10comprises a semiconductor element 1 that has a flat surface 2 formed byremoving an apex portion of a substantially spherical semiconductorcrystal 1 a made of a p-type semiconductor; an n⁺ type diffusion layer3; a substantially spherical pn junction 4 that is formed via thediffusion layer 3; a diffusion-mask thin film 5 made of a silicon oxidefilm; a pair of electrodes 6 a and 6 b (positive electrode 6 a, andnegative electrode 6 b); and an antireflection film 7, and so forth.Additionally, instead of above diffusion layer 3, semiconductorthin-film deposition layer can be applicable.

The semiconductor element 1 is made of a spherical semiconductor crystal1 a (see FIG. 1(a)) with a diameter of 1.5 mm, for example, made of ap-type silicon single crystal that has a resistivity of about 1 Ωcm.However, a substantially spherical semiconductor crystal 1 b withsubstantially the same diameter made of the silicon single crystal shownin FIG. 1(b) can also be adopted in place of the semiconductor crystal 1a.

As shown in FIG. 2, a flat surface 2 with a diameter of 0.7 mm to 0.9mm, for example, is formed at one of a pair of apexes that face eachother with the center of the semiconductor element 1 interposedtherebetween. The respective heights H of a multiplicity ofsemiconductor elements 1 of the same type are made uniform at a fixedheight that is 1.3 to 1.35 mm, for example. This serves to facilitateassembly in a semiconductor module 20, as will be describedsubsequently.

The n⁺ type diffusion layer 3 is formed over the majority of the surfaceof the semiconductor element 1 excluding the flat surface 2; thediffusion-mask thin film 5 (thickness 0.6 to 0.7 μm, for example) isformed on the flat surface 2 and in the vicinity of the perimeterthereof; and the diffusion layer 3 is not formed on the flat surface 2and in the vicinity of the perimeter thereof. The diffusion layer 3 is a0.4 to 0.5 μm thick n⁺ type diffusion layer in which phosphorus isdiffused as the n-type doping impurity. The substantially spherical pnjunction 4 (precisely, a pn⁺ junction) is formed on the semiconductorelement 1 via this diffusion layer 3. The positive electrode 6 a, whichelectrically is connected to the p-type silicon single crystal of thesemiconductor element 1 by penetrating the diffusion-mask thin film 5,is formed on the flat surface 2 of the semiconductor element 1. Thenegative electrode 6 b, which electrically is connected to the n-typediffusion layer 3 by penetrating the antireflection film 7, is formed atthe apex of the semiconductor element 1, on the opposite side of thepositive electrode 6 a with the center of the semiconductor element 1interposed between the negative electrode 6 b and the positive electrode6 a. The positive electrode 6 a is produced by causing an aluminum pasteto adhere to the semiconductor element 1 and then sintering this paste,while the negative electrode 6 b is produced by causing a silver pasteto adhere to the semiconductor element 1 and then sintering this paste.The antireflection film 7 consists of a phosphorus-containing siliconoxide film (of thickness 0.6 to 0.7 μm, for example). The antireflectionfilm 7 is formed so as to cover the whole surface of the semiconductorelement 1 excluding the diffusion-mask thin film 5, and, together withthe diffusion-mask thin film 5, covers substantially the whole surfaceof the semiconductor element 1. Further, the structure of thesemiconductor device 10 will also be made clearer from the descriptionof the making method of the semiconductor device 10 describedhereinbelow.

In the case of the semiconductor device 10, the substantially sphericalpn junction 4 has a photoelectric conversion function, performingphotoelectric conversion upon receipt of solar power to generate anelectromotive force whose maximum is approximately 0.6 volt between thepositive electrode 6 a and the negative electrode 6 b. The semiconductordevice 10 has a substantially spherical pn junction 4, the positiveelectrode 6 a being formed on the flat surface 2 and the negativeelectrode 6 b being formed in a position on the opposite side to thepositive electrode 6 a and in a position corresponding to the center ofthe diffusion layer 4. The semiconductor device 10 therefore also hasuniform optical sensitivity with respect to incident light from alldirections with the exception of the direction defined by the twoelectrodes 6 a and 6 b.

Due to the flat surface 2 being formed, and because the positiveelectrode 6 a is formed on the flat surface 2 and the negative electrode6 b is formed at the apex on the opposite side to the flat surface 2,the semiconductor device 10 is not prone to rolling. The flat surface 2permits adsorption when adsorbed by a vacuum pincette, a plurality ofsemiconductor elements 1 can be easily aligned with uniform orientation,and can be easily handled. Moreover, the positive electrode 6 a and thenegative electrode 6 b can be easily distinguished by means of a sensoror visual observation, whereby the operating efficiency when amultiplicity of the semiconductor device 10 is assembled in asemiconductor module can be raised. Moreover, there is no need to form aflat surface in order to form the negative electrode 6 b, and hence thesteps for the electrode formation can be reduced, this beingadvantageous also with respect to the reduction in the fabrication costsof the semiconductor element 1.

Next, the method for making the semiconductor device 10 will bedescribed with reference to FIGS. 1 to 8. Initially, as shown in FIG.1(a), a multiplicity of spherical or substantially sphericalsemiconductor crystals 1 a made of a p-type single crystal with adiameter of 1.5 mm and a resistivity of about 1 Ωm, for example, isfabricated. This spherical semiconductor crystal 1 a can be fabricatedby means of the method already proposed by the present inventors inJapanese Patent Laid Open application No. H10-33969 and InternationalPatent Publication No. WO98/15983, and so forth. In these methods, adrop tube is adopted and a sphere of a substantially spherical siliconsingle crystal is fabricated by causing silicon grains constituting thesource material to drop freely after being melted in a floating statewithin the upper end of the drop tube, while causing these grains tosolidify with the spherical shape maintained by the surface tension.Further, during the fabrication of the semiconductor crystal 1 a, minuteprotrusions and recesses, are sometimes generated in the semiconductorcrystal 1 a due to primary factors such as contraction duringsolidification. However, a spherical or substantially sphericalsemiconductor crystal may also be fabricated by chemical mechanicalpolishing method without using the drop tube.

Here, in place of the multiplicity of semiconductor crystals 1 a, amultiplicity of semiconductor crystals 1 b with the protrusion 1 c shownin FIG. 1(b) may be adopted. Although this semiconductor crystal 1 b hassame diameter and resistivity with those of the semiconductor crystal 1a, when the semiconductor crystal 1 b is fabricated, the semiconductorcrystal 1 b of substantially spherical silicon single crystal can bemade by burning silicon powder to a fine powder while guiding this finepowder into a fluidized bed reactor together with a fast-flowingmonosilane/hydrogen mixed gas and then decomposing the monosilane byheating same to 600 to 700° C., for example.

Next, as shown in FIG. 2, an apex part of the surface of thesemiconductor crystal 1 a (or the semiconductor crystal 1 b) issubjected to flat-surface processing by chemical mechanical polishing toform the flat surface 2 with a diameter of about 0.7 to 0.9 mm, wherebythe semiconductor element 1 shown in FIG. 2 is fabricated. Here, whenthe protrusion 1 c is present on the surface as in the case of thesemiconductor crystal 1 b, the flat surface 2 is formed by removing theprotrusion 1 c. When a protrusion or recess is present on the surface ofthe semiconductor crystal 1 a, the flat surface 2 is formed by removingthe protrusion or recess, and a semiconductor element 1 with a height Hof 1.3 to 1.35 mm is made. When the flat surface 2 is formed, apolishing process in a state where a multiplicity of the semiconductorcrystals 1 a (or semiconductor crystals 1 b) is fixed to a glass plateusing wax or a synthetic resin (wrapping process) is performed.Moreover, a polishing process is performed on a multiplicity ofsemiconductor crystals 1 a so that the respective heights H of amultiplicity of semiconductor elements 1 are equal at about 1.3 to 1.35mm, for example.

By forming the flat surface 2, in addition to allowing removal of partsof the surface of the semiconductor crystals 1 a and 1 b which exhibitunstable quality, the heights H of the multiplicity of semiconductorelements 1 can be made uniform, and hence such formation is advantageouswhen the semiconductor module 20 (described later) is fabricated.

Next, as shown in FIG. 3, the diffusion-mask thin film 5 (with a filmthickness of 0.6 to 0.7 μm, for example) consisting of a silicon oxidefilm is formed over the whole surface of the semiconductor element 1 bymeans of thermal oxidation.

Next, as shown in FIG. 4, an acid-resistant wax 9 is coated on anacid-resistant sheet 8, and, in a state where the wax is caused to meltby heating the same, the flat surface 2 of the multiplicity ofsemiconductor elements 1 is bonded by being made to contact theacid-resistant sheet 8 so as to adhere thereto. Next, the acid-resistantsheet 8, wax 9, and the multiplicity of semiconductor elements 1 areimmersed in etching solution, which is produced by mixing togetherhydrofluoric acid (HF) and ammonium fluoride (NH₄F), and thediffusion-mask thin film 5, which is not covered by the acid-resistantwax 9, is then removed by etching. When the wax 9 is then removed as aresult of being dissolved, the semiconductor element 1 shown in FIG. 5is obtained. In the case of the semiconductor element 1, thediffusion-mask thin film 5 remains only on the flat surface 2 of thesemiconductor element 1 and in the vicinity of the perimeter of the flatsurface 2.

Next, as shown in FIG. 6, in a state where the flat surface 2 and thevicinity of the perimeter thereof are masked by the diffusion-mask thinfilm 5, the n⁺ type diffusion layer 3 (depth of 0.4 to 0.5 μm) is formedby diffusing phosphorus (P), which is an n-type doping impurity, in thesurface of the semiconductor element 1 by means of a known method, and asubstantially spherical pn junction 4, which is located at a depth ofabout 0.4 to 0.5 μm from the surface of the semiconductor element 1, isthus formed.

During the phosphorus diffusion, the edge of the pn junction 4 diffusesbelow the diffusion-mask thin film 5 such that the concealed surface isprotected, and the surface where the diffusion-mask thin film 5 does notremain is formed with a thin silicon oxide film (with a film thicknessof about 0.4 μm, for example) containing phosphorus. The antireflectionfilm 7 is therefore formed by leaving the silicon oxide film as is.Hence, the step of forming the antireflection film 7 can be omitted,which is advantageous. However, the thickness of the antireflection filmmay be adjusted to an optimum value by depositing silicon dioxide on thesurface of the silicon oxide film by means of CVD. Thus, as shown inFIG. 6, a state is produced where the flat surface 2 of thesemiconductor element 1 and the vicinity of the perimeter thereof arethen covered by the diffusion-mask thin film 5 consisting of SiO₂ andthe remaining part of the surface is covered by the antireflection film7 consisting of phosphorus-containing SiO₂. Therefore, in order to formthe antireflection film 7, the optical input can be raised bysuppressing the reflection of light.

Next, as shown in FIG. 7, an aluminum paste 6A (with a diameter of 0.5mm and a thickness of 0.2 to 0.3 mm, for example) is coated on thesurface of the diffusion-mask thin film 5 of the flat surface 2 and asilver paste 6B (with a diameter of 0.5 mm and a thickness of 0.2 to 0.3mm, for example) is coated on the apex on the opposite side facing theflat surface 2 with the center of the semiconductor element 1 interposedbetween the aluminum paste 6A and the silver paste 6B, and then thesepastes 6A, 6B are dried by being heated to approximately 150° C.Thereafter, as detailed above, the multiplicity of semiconductorelements 1, which have each been provided with the aluminum paste 6A andthe silver paste 6B as described above, are accommodated in the nitrogengas atmosphere of an electric furnace so as to be heated and sinteredfor approximately 30 minutes at a temperature of approximately 800 to850° C. Accordingly, as shown in FIG. 8, the positive electrode 6 a isproduced as a result of the aluminum paste 6A penetrating thediffusion-mask thin film 5 to make low resistance contact with thep-type silicon single crystal, and the negative electrode 6 b isproduced as a result of the silver paste 6B penetrating theantireflection film 7 to make low resistance contact with the diffusionlayer 3, the positive electrode 6 a and the negative electrode 6 b beinglocated substantially symmetrically such that the center of thesemiconductor element 1 is interposed therebetween. A spherical orsubstantially spherical light receiving semiconductor device 10 that issuitable as a solar cell (light receiving device) is thus finished.

When the pastes are applied, the aluminum paste 6A may be coated on theflat surface 2 and hence the application position is not mistaken. Thesilver paste 6B may be applied at the apex on the opposite side to thealuminum paste 6A, and hence a mistake with the application position isnot made.

As shown in FIGS. 20 to 27 of the International Patent Publication No.WO 98/15983, this spherical-surface light receiving-type semiconductordevice 10 can be housed independently in a glass package or a syntheticresin package, or can be housed in a glass package or a synthetic resinpackage, as an array in which a plurality of semiconductor devices 10 isconnected in series and is connected to an external circuit. Thesemiconductor device 10 can be put to practical use as a light receivingdevice (capable of receiving light from all directions) with barely anydirectivity.

Further, a flexible, sheet-like light receiving semiconductor module canalso be produced by disposing semiconductor devices 10 in the form of amatrix with multiple rows and columns in which the multiplicity ofsemiconductor elements 1 of each column is electrically connected inseries and the multiplicity of semiconductor elements 1 of each row iselectrically connected in parallel, all these semiconductor devices 10then being embedded in a transparent synthetic resin. Likewise, acylindrical sheet-like or cylindrical rod-like light receivingsemiconductor module can also be constituted. Further, as a structure inwhich a plurality of semiconductor elements 1 is electrically connected,a structure in which the plurality of semiconductor elements 1 isconnected by means of an electrically conductive epoxy resin can also beadopted.

During the above electrode formation, by applying the aluminum paste 6Ato the surface of the diffusion-mask thin film 5 and applying the silverpaste 6B to the surface of the antireflection film 7 and then heatingand sintering the pastes, the positive electrode 6 a, which is connectedto a p-type conductor, and a negative electrode 6 b, which is connectedto the diffusion layer 3, are formed. The method or process for theelectrode formation can thus be simplified. Moreover, the silicon oxidefilm that is formed during the formation of the diffusion layer 3 iseffectively put to practical use as the antireflection film 7, and hencethe number of steps for fabricating the semiconductor device 10 can besmall and the fabrication costs can be remarkably reduced.

Next, a description will be provided for the structure and the makingmethod of a low-cost resin mold-type light receiving semiconductormodule 20 (solar cell module) that is suitable to mass production byusing the semiconductor device 10 which is a solar cell fabricated asabove. First of all, the structure will be described with reference toFIGS. 16 and 17. This light receiving semiconductor module 20 isactually constituted mainly from the semiconductor devices 10 disposedin the form of a matrix with multiple rows and columns. However, inorder to simplify the description, the same is provided by taking anexample of a light receiving semiconductor module that uses twenty-fivesemiconductor devices 10 disposed in 5 rows and 5 columns, for example.The light receiving semiconductor module 20 comprises twenty-fivesemiconductor devices 10; a conductive connection mechanism 27 whichcomprises six connecting leads 21 to 26 and electrically connects thetwenty-five semiconductor devices 10; a light transmitting member 28;and a positive terminal 29 a and a negative terminal 29 b.

The twenty-five granular semiconductor devices 10 are disposed in fiverows and five columns in a state where the conduction direction isaligned to the direction of column, a plurality of semiconductor devices10 of each column being electrically connected in series by theconductive connection mechanism 27 and a plurality of semiconductordevices 10 of each row being electrically connected in parallel. Theconductive connection mechanism 27 is constituted by six metalconnecting leads 21 to 26. The six connecting leads 21 to 26 comprisethe connecting lead 21 connected to the positive electrodes 6 a on theunderside of the semiconductor devices 10 of the lowermost row;connecting leads 22 to 25, which are mounted between the semiconductordevices 10 of each row and the semiconductor devices 10 of the rowadjoining the top face of the semiconductor devices 10 of each row; andthe connecting lead 26 connected to the negative electrode 6 b on thetop face of the semiconductor devices 10 of the uppermost row. Each ofthe connecting leads 22 to 25 connects the negative electrodes 6 b of alower semiconductor devices 10 and the positive electrodes 6 a of anupper semiconductor devices 10. Accordingly, the semiconductor devices10 of each column are serially connected by the connecting leads 22 to25, while the semiconductor devices 10 of each row are connected inparallel by the connecting leads 21 to 26.

The twenty-five semiconductor devices 10 and the conductive connectionmechanism 27 are packaged in an embedded state in a light transmittingmember 28 consisting of a transparent synthetic resin such as an acrylicresin or polycarbonate, for example, a partial cylinder lens portion 28a that guides extrinsic light from both sides to the semiconductordevices 10 in each column being formed on the light transmitting member28. An electrical circuit that is equivalent to the light receivingsemiconductor module 20 constituting this solar cell panel is as shownin FIG. 18.

The structure is such that the light receiving semiconductor module 20is embedded in the light transmitting member 28 consisting of atransparent synthetic resin, the twenty-five semiconductor devices 10and the connecting leads 21 to 26 are rigidly packaged, and are superiorin strength and durability. The partial cylinder lens portion 28 a ofthe light transmitting member 28 serves to efficiently introduceextrinsic light into the semiconductor devices 10 of each column, and,in comparison with a case where the surface of the semiconductor module20 is formed as a flat surface, possesses wide directivity and issuperior in lighting and light-gathering. Moreover, the refractive indexof the light of the light transmitting member 28 is greater than 1.0,and hence the light entering the light transmitting member 28 isrepeatedly reflected at the surface of the partial cylinder lens portion28 a and is easily absorbed by the semiconductor devices 10. Moreparticularly, the refractive index of glass and of a transparentsynthetic resin such as acrylic or polycarbonate is greater than therefractive index of air, and therefore the incident light from theoutside is diffused by the diffused reflection within the lighttransmitting member 28 and widely scattered. The semiconductor devices10 housed within the light transmitting member 28 are capable ofabsorbing light in every direction, and hence exhibit high light usageefficiency in comparison with a solar cell panel with a conventionalone-sided flat structure, and generate a large photovoltaic effect.

Because the semiconductor module 20 comprises the above-mentionedconductive connection mechanism 27, even when any semiconductor device10 exhibits a functional loss or stops functioning due to failure or ashadow, because the output of a normal semiconductor device 10 is outputby being shunted via another normal semiconductor devices 10 that are ina parallel connection, there is hardly any adverse effect caused by thefailure or functional loss of some semiconductor devices 10, which makesthe light receiving semiconductor module 20 superior in reliability anddurability. Moreover, a plurality of semiconductor devices 10 can beconnected in series and in parallel via a simple-structure conductiveconnection mechanism 27.

Next, a method for fabricating the above-described light receivingsemiconductor module 20 (solar cell module) will be described withreference to FIGS. 9 to 15.

First of all, the above-mentioned multiplicity of semiconductor devices10 is fabricated and, at the same time, as shown in FIG. 9, the surfaceof a thin plate (about 0.3 mm thick) of an iron-nickel alloy (Fe 56%, Ni42%) is silver-plated or nickel-plated to a thickness of about 3 μm, andthe thin plate is punched with a die, whereby the flat-plate-like leadframes 21A to 26A with four openings 30 a and 30 b are fabricated. Anouter frame portion 31 with a width of about 4 mm and three mutuallyparallel connecting leads 21 that are 0.5 mm thick, for example, areformed in the lead frame 21A. The other lead frames 22A to 26A are alsoformed in this manner.

Next, as shown in FIGS. 9 to 13, an aluminum paste 32 (with a diameterof 0.5 mm, and a thickness of 0.2 to 0.3 mm) is printed at five pointson the upper surface of the connecting leads 21 to 25 of the lead frames21A to 25A respectively, and a silver paste 33 (with a diameter of 0.5mm and a thickness of 0.2 to 0.3 mm) is printed at five points on thelower surface of the connecting leads 22 to 26 of the lead frames 22A to26A respectively. Next, semiconductor devices 10 are placed, withkeeping the positive electrodes 6 a downward, on the aluminum paste 32of the respective connecting leads 21 of the lead frames 21A. Next, thelead frame 22A is placed on the fifteen semiconductor devices 10 of thefirst row, and the fifteen negative electrodes 6 b are caused to makecontact with the silver paste 33 of the connecting lead 22. Thereafter,as described above, the lead frames 23A to 26A and semiconductor devices10 are sequentially placed, and, the lead frames 21A to 26A are used toplace 25×3 semiconductor devices 10 in the form of the 3 sets of 5×5matrices shown in FIG. 13, whereby an assembly body 30 is made.Thereafter, in a state where a predetermined weight is placed on theuppermost-level lead frame 26A, the aluminum paste 32 and the silverpaste 33 are cured by being housed within the heating oven and heated ata temperature of about 160 to 180° C.

Accordingly, the twenty-five semiconductor devices 10 of each set (eachmodule) are electrically connected via the six lead frames 21A to 26A,so that a total of 75 semiconductor devices 10 of three sets arecontained in an orderly fashion between the connecting leads 21 to 26 ofthe six lead frames 21A to 26A. The twenty-five semiconductor devices 10of each module 20 thus assume a state where the semiconductor devices 10of each column are electrically connected in series by the connectingleads 21 to 26 and where the semiconductor devices 10 of each row areelectrically connected in parallel by the connecting leads 21 to 26.

Next, as shown in FIGS. 14 to 15, the assembly body 30 of seventy-fivesemiconductor devices 10 and six lead frames 21A to 26A is housed withina mold (not illustrated) and molded as shown by using a transparentsynthetic resin (such as acrylic resin or polycarbonate, for example).The semiconductor devices 10 in 5 rows and 5 columns of each settogether with the corresponding connecting leads 21 to 26 are embeddedwithin the light transmitting member 28 and packaged by the lighttransmitting member 28. Three sets of light receiving semiconductormodules 20 constituting solar cell panels are thus molded at the sametime. A partial cylinder lens portion 28 a, which focuses extrinsiclight from both sides onto the semiconductor devices 10 in each column,is formed on the light transmitting member 28. Further, the two ends ofthe connecting leads 21 to 26 protrude to the outside of the lighttransmitting member 28.

Finally, when the three sets of light receiving semiconductor modules 20are decoupled from the outer frame 31 of the six lead frames 21A to 26A,the light receiving semiconductor modules 20 shown in FIGS. 16 and 17are obtained.

First Modified Embodiment

In this embodiment, a description is made for an example in which theassembly body 30 is assembled after the positive electrode 6 a and thenegative electrode 6 b have been formed on each semiconductor device 10.However, as will be described next, the positive electrode 6 a and thenegative electrode 6 b could also be formed during the assembly of theassembly body 30. That is, the aluminum paste 32 (with a diameter of 0.5mm and a thickness of 0.2 to 0.3 mm) is printed as shown in FIG. 10 atfive points on the upper surface of the connecting leads 21 to 25 ofeach of the lead frames 21A to 25A, and the flat surface 2 of thesemiconductor device 10 not formed with electrodes is made to makesurface contact atop the respective aluminum paste 32. In this state,the lead frames 21A to 25A together with the fifteen semiconductordevices 10 on the lead frames 21A to 25A are heated to 150° C. in aheating oven so as to cure the aluminum paste 32, whereby thesemiconductor devices 10 are made to adhere to the connecting leads 21to 25.

Next, silver paste 33 (with a diameter of 0.5 mm and a thickness of 0.2to 0.3 mm) is applied to the respective apex (the apex opposite to theflat surface 2 such that the center of the semiconductor device 10 isinterposed therebetween) of the fifteen semiconductor devices 10 stuckto the lead frames 21A to 25A, and the corresponding lead frames 22A to26A atop the fifteen semiconductor devices 10 of the lead frames 21A to25A respectively (the lead frames 22A to 25A to whose upper side thesemiconductor devices 10 are stuck, and the lead frame 26A to which asemiconductor device 10 is not stuck) are placed with the two edges ofthe outline of the lead frames 22A to 26A serving as a reference. Theconnecting leads 22 to 26 are assembled in the assembly body 30 shown inFIG. 13 by being made to contact the silver paste 33. The assembly body30 is then heated to 150° C. in a heating furnace to cure the silverpaste and to stick the semiconductor devices 10 to the connecting leads22 to 26.

Next, the assembly body 30 is housed within the heating furnace andheated for approximately 30 minutes at a temperature of 800 to 850° C.in a nitrogen atmosphere. As a result of this heating, thediffusion-mask thin film 5 of each semiconductor device 10 is destroyedby the heat and the aluminum paste enters a state of being connected tothe p-type silicon semiconductor, such that the aluminum paste forms thepositive electrode 6 a. At the same time, the antireflection film 7 ofeach semiconductor device 10 is destroyed by the heat and the silverpaste enters a state of being connected to the n type diffusion layer 3,whereby the silver paste forms a negative electrode 6 b. Accordingly,the assembly body 30 shown in FIG. 13 is then finished. With thismethod, the step of forming each semiconductor device 10 with thepositive and negative electrodes 6 a and 6 b is omitted, it will bepossible to form the electrodes 6 a and 6 b in parallel with theassembly of the assembly body 30. This is therefore advantageous onaccount of the reduction in the costs of fabricating the semiconductormodule 20.

Second Modified Embodiment

(see FIGS. 19 and 20)

In this embodiment, the assembly body 30 is housed within a mold andthree sets' worth of semiconductor modules 20 are molded by pouring atransparent synthetic resin into the mold, whereupon each semiconductormodule 20 is decoupled from the outer frame 31. However, three sets'worth of semiconductor modules 20 need not necessarily be molded in thismanner. As shown in FIGS. 19 and 20, the twenty-five×three semiconductordevices 10 and the connecting leads 21 to 26 are housed within a moldwith a cube-shaped mold cavity and a transparent synthetic resin ispoured into the mold and solidifies such that a cube-shapedsemiconductor module 20A in which the seventy-five semiconductor devices10 are three-dimensionally housed in a substantially cube-shaped lighttransmitting member 28A may be molded. Further, a partial cylinder lensportion 28 a like the above-mentioned partial cylinder lens portion 28 ais desirably formed on the outside of the cube-shaped semiconductormodule 20A. So too in the case of the semiconductor module 20A,although, in order to simplify the description, the same was made bytaking, as an example, a case where the semiconductor devices 10 arearranged in a five row by five column matrix, there are also cases wherethe semiconductor devices 10 are arranged in the form of a matrix ofmultiple rows and multiple columns and this matrix is then molded toform the cube-shaped semiconductor module 20A.

In the case of the cube-shaped semiconductor module 20A, the multiplesemiconductor devices 10 are arranged three-dimensionally in the lighttransmitting member 28A, and hence light from every direction withinthree dimensions is received and photoelectrically converted. Moreover,because this multiplicity of semiconductor devices 10 has a largesurface area for receiving light, this multiplicity of semiconductordevices 10 possesses a light receiving capacity that is large incomparison with the semiconductor module 20. A portion of the lightentering the light transmitting member 28A reaches directly to theserially connected semiconductor devices 10, while the remaining lightreaches to the semiconductor devices 10 after repeatedly undergoingdiffused reflection and scattering. For this reason, the light usageefficiency can be remarkably improved than a conventional solar cellpanel. Further, the cube-shaped semiconductor module 20A can beconstituted in the form of a sheet and a semiconductor module with astructure in which the semiconductor devices 10 are incorporated in aplurality of layers within a transparent and flexible light transmittingmember can also be implemented.

Third Modified Embodiment

(see FIGS. 21 and 22)

Next, a description will be provided for a modified embodiment of thesemiconductor module with a light receiving function that utilizes thesemiconductor device 10. As shown in FIGS. 21 and 22, this semiconductormodule 40 comprises eighty (16×5) semiconductor devices 10, for example,which function to perform an photoelectric conversion upon receivinglight; a conduction mechanism 50, which comprises six metal circularlead frames 41 to 46; and a light transmitting member 48. However, thesemiconductor devices 10 are the same as the semiconductor devices 10 ofthe semiconductor module 20.

The circular lead frames 41 to 46 are formed integrally with each of theinside connecting leads 41 a to 46 a and the outside connecting leads 41b to 46 b, and four external leads 41 c to 46 c, which protrude towardthe outside in the radial direction, are formed on the outsideconnecting leads 41 b to 46 b. Forty semiconductor devices 10 areconnected to the inside connecting leads 41 a to 46 a (width 0.8 mm, forexample) at equal intervals in the circumferential direction by beinggrouped into eight columns such that the conduction direction is uniformby aligned, and the remaining forty semiconductor devices 10 areconnected to the outside connecting leads 41 b to 46 b (width 0.8 mm,for example) at equal intervals in the circumferential direction bybeing grouped into eight columns such that the conduction direction isuniform by aligned.

The conductive connection mechanism 50 comprises a lowermost-levelcircular lead frame 41, middle-level circular lead frames 42 to 45, andan uppermost-level circular lead frame 46. The circular lead frames 41to 46 are of the same plate thickness and same quality as the leadframes (21 to 26) of the above embodiments. An external lead 41 c of thelowermost-level circular lead frame 41 is a positive electrode terminal47 a and an external lead 46 c of the uppermost-level circular leadframe 46 is a negative electrode terminal 47 b.

Similarly to the semiconductor module 20, each of the circular leadframes 41 to 45 is connected by aluminum paste to the positive electrode6 a of an upper semiconductor device 10, and each of the circular leadframes 42 to 46 is connected by silver paste to the negative electrodes6 b of a lower semiconductor devices 10. Accordingly, the conductiveconnection mechanism 50 is such that five semiconductor devices 10 ofeach column are electrically connected in series, and sixteensemiconductor devices 10 of each level are electrically connected inparallel.

An assembly body 51, which is produced by assembling the six circularlead frames 41 to 46 and eighty semiconductor devices 10, is embeddedwithin the cylindrical light transmitting member 48. However, the outerends of the external leads 41 c to 46 c protrude to the outside. Thelight transmitting member 48 consists of a transparent synthetic resinsuch as acrylic or polycarbonate. Conical recesses 48 a and 48 b, whichserve to raise the light introduction rate, are formed in the middle ofthe lower and upper end faces of the light transmitting member 48.Partial conical chamfered sections 49 a and 49 b, which serve to raisethe light introduction rate, are formed on the respective outercircumference of the lower and upper ends of the light transmittingmember 48.

The method of fabricating this semiconductor module 40 will now bedescribed. First of all, the circular lead frames 41 to 46 and theeighty semiconductor devices 10 are fabricated and prepared. Next,substantially the same manner as the semiconductor module 20 wasadopted, the assembly body 51 is assembled by assembling the circularlead frames 41 to 46, the eighty semiconductor devices 10, and thealuminum paste and silver paste, and so forth.

Next, the aluminum paste and silver paste are cured by housing theassembly body 51 in a heating oven and subjecting the assembly body 51to a heat treatment for approximately 30 minutes at a temperature of 800to 850° C. in a nitrogen atmosphere. Next, the assembly body 51 ishoused in a mold, and, when a dissolved transparent synthetic resin(acrylic resin or polycarbonate, for example) is poured into the moldand solidifies, the semiconductor module 40 is obtained.

Further, as per the first modified embodiment, so too when thesemiconductor module 40 is fabricated, the positive and negativeelectrodes 6 a and 6 b may be formed in parallel with the assembly of anassembly body 60 by using semiconductor devices 10 with no electrode, ormay be formed after assembling the assembly body 60.

Because the semiconductor module 40 is formed so as to have acylindrical shape as a whole, even in a case where the extrinsic lightcomes from any direction within the 360 degrees of the fullcircumference, this light is reliably introduced to the lighttransmitting member 48, and the extrinsic light from above or below thesemiconductor module 40, is also reliably introduced to the lighttransmitting member 48. The light thus introduced into the lighttransmitting member 48 is scattered via diffused reflection while beingphotoelectrically converted upon reaching the semiconductor device 10,thereby generating an electromotive force on the order of approximately3.0 volts between the positive electrode terminal 47 a and the negativeelectrode terminal 47 b.

Fourth Modified Embodiment

(see FIGS. 23 to 29)

A modified embodiment of the light receiving semiconductor module willnow be described along with the making method and structure thereof.First of all, the base sheet 60 shown in FIG. 23 is fabricated. The basesheet 60 is a flat-plate-like transparent sheet of a predetermined size(200 mm×200 mm, for example) made of a transparent synthetic resin(acrylic or polycarbonate, for example) with a thickness of 0.4 to 0.6mm. Square small holes 61 with the dimensions 1.5 mm×1.5 mm, forexample, which serve to mount semiconductor devices 10 like those of thesemiconductor device 10 in FIG. 8, are formed in the form of a matrixwith multiple rows and multiple columns, vertical frames 62 with a widthof 0.8 to 1.0 mm being formed between one column of small holes and thenext column, and connecting lead formation sections 63 with a width of0.4 to 0.6 mm being formed between one row of small holes and the nextrow. The small holes 61 are desirably formed having a size and shapesuch that a plurality of points on the equator midway between thepositive and negative electrodes 6 a and 6 b of the semiconductordevices 10 make light point contact and are trapped. The shape of thesmall holes is not restricted to a square. Rather, a variety of shapescan be adopted.

The base sheet 60 can be fabricated by means of extrusion molding orsimilar by using a precise molding die, but could also be fabricated byboring with a laser beam of an excimer laser in a state wherepredetermined masking is performed on a sheet-like or film-like basesheet member, or may be fabricated by means of another method.

Next, as shown in FIG. 24, at least a single side of the multipleconnecting lead formation section 63 and sections facing the small holes61 are formed with a transparent conductive synthetic resin or a metalconductive film 64 a (with a thickness of 10 to 30 μm, for example),whereby the connecting lead 64 is produced. A conductive synthetic resinor a metal conductive film 66 a (with a thickness of 10 to 30 μm, forexample) is formed at one end of the base sheet 60 in the columndirection thereof and on the external conductive wire connection portion65 at the other end, and the conductive film 66 a is formed in thesection facing the small holes 61, whereby a connecting lead 66 isproduced. Further, when the metal conductive films 64 a and 66 a areformed, the same may be formed by a nickel plating film, for example. Inaddition, a multiplicity of semiconductor devices 10 like those shown inFIG. 8 is fabricated prior to or in parallel with the fabrication of thebase sheet 60.

Next, as shown in FIGS. 25 and 26, a semiconductor device 10 is mountedin each of a multiplicity of small holes 61 in a state where the basesheet 60 is set in a state of floating approximately 0.5 mm above asuitable horizontal base plate. In this case, a conductive adhesive orconductive paste (aluminum paste, silver paste, gold paste, or the like)is applied to the positive electrode 6 a and the negative electrode 6 bof the semiconductor device 10, and the semiconductor device 10 ismounted in the small hole 61 in a state where the respective conductiondirections of all the semiconductor devices 10 are uniform and where thepositive and negative electrodes 6 a and 6 b make surface contact withthe corresponding conductive films 64 a and 66 a, the semiconductordevice 10 being made to protrude substantially equally outside bothsides of the base sheet 60. Thereafter, where required, the conductiveadhesive and conductive paste on the electrodes 6 a and 6 b may be curedby being irradiated with laser light.

A conductive connection mechanism that comprises a multiplicity ofconnecting leads 64 and 66, and a conductive paste, or the like, whichconnects the electrodes 6 a and 6 b of the semiconductor device 10 tothe connecting leads, is constituted. As a result of this conductiveconnection mechanism, semiconductor devices 10 of each column areconnected in series and semiconductor devices 10 of each row areconnected in parallel.

Next, as shown in FIG. 27, an assembly body 67, in which the base sheet60 and a multiplicity of semiconductor devices 10 are assembled, ishoused within a predetermined mold, and, when molding is performed bypouring a dissolved transparent synthetic resin (acrylic, polycarbonate,or the like, for example) into the mold, the base sheet 60 and themultiplicity of semiconductor devices 10 are embedded within a lighttransmitting member 68 consisting of a synthetic resin, whereby asubstantially transparent sheet- or film-like semiconductor module 70 isobtained. Further, for an external conductive wire connection, part ofan external conductive wire connection portion 65 at both ends of thebase sheet 60 is molded in a state of protruding from the lighttransmitting member 68.

The average film thickness of the synthetic resin applied during thismolding may be 0.5 to 1.0 mm, for example, but is not limited to thisfilm thickness. Rather, the film thickness can be determined freely. Asfor the synthetic resin provided in the molding process, a syntheticresin of the same type as the base sheet 60 is desirably adopted.However, a different type of synthetic resin may also be adopted, and,by suitably selecting the synthetic resin provided in this molding, aflexible semiconductor module 70 can also be rendered. Further, when aconductive paste is adopted for the positive and negative electrodes 6 aand 6 b of the semiconductor device 10, curing of the conductive pastecan also be achieved by means of the heat of the synthetic resininjected during molding.

In the case of the semiconductor module 70, in order to raise the lightintroduction capacity (lighting-gathering capacity), molding isperformed such that the outside part corresponding with thesemiconductor devices 10 of each column is a partial cylinder face 69.The partial cylinder face 69 may be formed only on one side, while theother side may be formed as a flat surface. Further, molding may beperformed such that the outside part that corresponds with eachsemiconductor device 10 of the semiconductor module 70 is apartial-sphere surface. The partial-sphere surface may be formed on onlyone side, while the other side may be formed as a flat surface.

Here, as shown in FIG. 28, two assembly bodies 67 are placed closetogether parallel to each other by being shifted by a half pitch in therow direction and/or column direction. In this state, the assemblybodies 67 are housed in a mold as described above, and, when a lighttransmitting member 68A is formed as a result of the assembly bodies 67being integrally molded by using a transparent synthetic resin, asemiconductor module 70A is obtained. Further, in the case of thesemiconductor modules 70 and 70A, an optical reflection film such as anickel plating film may be formed on the outside on the opposite side tothe entering direction of the incident light.

According to the semiconductor modules 70 and 70A of this embodiment, inaddition to actions and effects like those of the semiconductor modules20, 20A, 40, being obtained, specific actions and effects are alsoobtained. The semiconductor modules 70 and 70A are fabricated in sheetform by forming connecting leads 64 and 66 on the base sheet 60, whichcan be fabricated at low cost, mounting a multiplicity of semiconductordevices 10, and then forming synthetic-resin light transmitting members68 and 68A by means of injection molding and so forth. Hence, asheet-like or film-like lightweight semiconductor module is produced,fabrication costs can be reduced, and a high output or high voltagephotovoltaic effect can be generated by means of a multiplicity ofsemiconductor devices 10.

The semiconductor modules 70 and 70A can also be fabricated with athickness of 2.0 to 3.0 mm, and a solar cell panel (solar cell sheet)that can be stuck on window glass can also be implemented. Moreover,flexible semiconductor modules 70 and 70A can also be constituted, itwill be possible to fabricate semiconductor modules 70 and 70A that canbe applied to a variety of applications such as a semiconductor modulethat can be mounted on the body surface of an automobile.

More particularly, where the semiconductor module 70A is concerned,because semiconductor devices arranged in a matrix shape areincorporated in a two-layer structure, light entered in the lighttransmitting member 68A is easily absorbed by the semiconductor device10, thereby raising the light usage efficiency.

Next, an example in which this modified embodiment is modified in partwill be described simply on the basis of FIGS. 29 and 30. As shown inFIGS. 29 and 30, a multiplicity of substantially semispherical smallrecesses 72 are formed in the form of a matrix with multiple rows andmultiple columns on a base sheet 71 (with a thickness of 1.5 to 2.0 mm,for example) made of a transparent synthetic resin such as acrylic orpolycarbonate, for example. An optical reflection film 73 such as anickel plating film, for example, may be formed, on the rear side of thebase sheet 71. But the optical reflection film 73 may be omitted.Further, the base sheet 71 may be constituted by a soft transparentsynthetic resin material.

The small recesses 72 are formed such that half of the semiconductordevices 10 on the one side can be fitted at a minute gap or without agap, and are formed with a flat section 72 a that conforms with theshape of the flat surface 2 of the semiconductor device 10. Further,retaining portions 74, which serve to provide a hold, by way of surfacecontact with the positive and negative electrodes 6 a and 6 b, areformed so as to protrude upright approximately 0.4 mm to the front sideof the page of FIG. 29, at both ends of the small recesses 72 in thecolumn direction thereof. Multiple row connecting leads with the samestructure as the connecting leads 64 and 66 are formed on the base sheet71 and the semiconductor devices 10 are mounted in each of the smallrecesses 72, such that the positive electrodes 6 a and negativeelectrodes 6 b are connected to corresponding connecting leads so as tobe capable of conducting electricity thereto, and are fixed firmly.Here, the constitution may be such that the retaining force of theretaining portions 74 is used to retain the semiconductor devices 10.Further, in order to facilitate the formation of the connecting leads,the retaining portions 74 of each row may be formed continuously.Similarly to the connecting leads 64 and 66, the connecting leads formedin multiple rows constitute a conductive connection mechanism wherebythe multiplicity of semiconductor devices 10 of each column areconnected in series and the semiconductor devices 10 of each row areconnected in parallel.

Next, an assembly body 75 that is produced by mounting a multiplicity ofsemiconductor devices 10 on the base sheet 71, is housed in apredetermined mold and molding is performed by pouring a transparentsynthetic resin into the mold. A transparent and soft synthetic resinmaterial may be used as the synthetic resin provided in this molding.Accordingly, a multiplicity of semiconductor devices 10 become a stateof being embedded in a light transmitting member 77 that consists of thebase sheet 71 and a synthetic resin 76 that is poured into the mold andsolidifies. A lightweight, light receiving semiconductor module 70B(solar cell sheet, solar cell film, or solar cell panel) that is in theform of a sheet or film is thus obtained. Further, a partial cylindersurface that is similar to the partial cylinder face 69, or apartial-sphere surface, or the like, may be formed in the outer surfaceof the light transmitting member (76) that is formed by the molding.With the semiconductor module 70B, actions and effects like those of thesemiconductor modules 70 and 70A are obtained.

Fifth Modified Embodiment

(FIGS. 31 to 34).

FIG. 34 is a cross-sectional view of a semiconductor device 80constituting a spherical light receiving cell. The fabrication methodand structure of the semiconductor device 80 will now be described onthe basis of FIGS. 31 to 34.

The semiconductor element 81 shown in FIG. 31 is the same as thesemiconductor element 1 shown in FIG. 5. One flat surface 83 is formedon a spherical p-type silicon single crystal 82, and, before a thin-filmn⁺ silicon growth layer 85 is grown on the surface of the silicon singlecrystal 82, a mask thin film 84 (silicon oxide film), which serves as amask during the growth of the thin-film single crystal, is formed in thesame manner as in the above embodiment on the flat surface 83 and in thevicinity thereof. Further, where required, a silicon nitride film(Si₃N₄) may be formed on the outside of the mask thin film 84.

Next, as shown in FIG. 32, an n⁺ type growth layer 85 (this isequivalent to a semiconductor thin-film deposition layer) with a uniformfilm thickness (for example, 0.5 to 1.5 μm) is grown on the surface ofthe externally exposed p-type silicon single crystal 82 by usinghot-wall type atmospheric pressure Chemical Vapor Deposition (CVD) inwhich the source gases are known dichlorosilane (SiH₂Cl₂) and monosilane(SiH₄), for example. Accordingly, a spherical pn junction 86 is formedat the surface of the p-type silicon single crystal 82. Next, the maskthin film 84 is removed by using a known etching method and then thewhole surface is lightly etched (with a thickness of 0.1 to 0.2 μm, forexample). Thereafter, a silicon oxide film with a thickness of 0.4 to0.5 μm is once again deposited (formed) and, as shown in FIG. 33, asubstantially spherical antireflection film 87 is formed.

In addition to a silicon oxide film, a thin film of titanium oxide,silicon nitride, aluminum oxide or magnesium fluoride, or the like, canalso be adopted as the antireflection film 87.

Next, similar to the above embodiments, a positive electrode 88 a and anegative electrode 88 b are formed in the middle of the flat surface 83and at the apex of the spherical surface facing the flat surface 83respectively, such that the center of the semiconductor element 81 isinterposed therebetween. This semiconductor device 80 (aspherical-surface light receiving cell) also affords substantially thesame photoelectric conversion function as the semiconductor device 10 inFIG. 8, and possesses wide directivity.

Sixth Modified Embodiment

(see FIGS. 35 to 38)

FIG. 38 is a cross-sectional view of an npn phototransistor 90(semiconductor device) that has a substantially spherical lightreceiving surface. A description of the making method and structure ofthis npn phototransistor 90 will now be made on the basis of FIGS. 35 to38.

The semiconductor element 91 shown in FIG. 35 is an element produced byforming a flat surface 93 at one apex of the spherical n-type siliconsingle crystal 92 (resistivity 1 to 10 Ωcm), and then forming a borondiffusion mask thin film 94 (silicon oxide film) on the flat surface 93and in the vicinity thereof The semiconductor element 91 differs only inthat the n-type silicon single crystal 92 is applied in place of thep-type silicon single crystal in FIG. 5 of the above embodiment, and cantherefore be fabricated in substantially the same manner as thesemiconductor element 1 in FIG. 5.

Next, a p-type base layer 95 is formed on the surface of the n-typesilicon single crystal 92 by diffusing boron (to a depth of 0.3 to 0.5μm, for example), which constitutes the p-type impurity, by knownthermal diffusion. Accordingly, a substantially spherical collectorjunction 96 is formed between the p-type base layer 95 and an n-typecollector 92 a consisting of the n-type silicon single crystal 92. Athin silicon oxide film 97, which is generated when the boron isdiffused, is removed by means of a known etching technique together withthe diffusion mask thin film 94. Thereafter, as shown in FIG. 37,silicon oxide films 98 and 98 a are provided once again over the wholesurface. In order to use silicon oxide film 98 as a mask for thephosphorus diffusion on top of the surface of the p-type base layer 95,and the silicon oxide film 98 is removed by a known photoetchingtechnique, leaving the silicon oxide film 98 a on the flat surface 93and in the vicinity thereof. Further, the flat surface 93 can be used toalign the part to be masked.

Next, a substantially spherical n-type emitter layer 99 is formed in theregion of the p-type base layer 95 by diffusing phosphorus (to a depthof 0.1 to 0.2 μm, for example) which constitutes the n-type impurity bymeans of known thermal diffusion technique. Accordingly, as shown inFIG. 37, an emitter junction 100, which keeps a fixed interval (forexample, 0.1 to 0.4 μm) from the collector junction 96, is formedbetween the n-type emitter layer 99 and the p-type base layer 95. Thethin silicon oxide film generated during the phosphorus diffusion isused as an antireflection film 101. Next, a collector electrode 102 andan emitter electrode 103 are provided as shown in FIG. 38 by using asilver paste and an aluminum paste as used for the semiconductor element1 of the above embodiments. The electrodes 102 and 103 may be formed soas to be usable as a junction with an external electrically conductivemember such as a lead frame.

The substantially spherical npn phototransistor 90 (equivalent to alight receiving semiconductor device) has a spherical surface of whichthe majority is a light receiving surface, such that when incident lightfrom outside is absorbed in the vicinity of the collector junction 96 ina state of reverse bias, an optical current is generated and anamplified external current flows between the emitter electrode 103 andthe collector electrode 102. This phototransistor 90 can be used as anoptical switch or the like and has characteristics such as high lightreceiving sensitivity and wide light directivity.

Next, descriptions will be made for various modified embodimentspartially modifying the above embodiments.

1) A silicon polycrystal can also be adopted as the semiconductorconstituting the semiconductor elements 1, 81, 91, or, instead ofsilicon, another semiconductor, such as an Si and Ge mixed-crystalsemiconductor, or a multilayered structure semiconductor may be adopted,for example. Any compound semiconductor such as GaAs, InP, GaP, GaN,InCuSe, or SiC may be adopted and another semiconductor may beapplicable.

2) The diameter of the semiconductor crystal forming the semiconductorelement 1 is not limited to 1.5 mm. Rather, there are also cases wherethe diameter has a magnitude on the order of 0.5 to 3.0 mm. Further, theconductivity type of the semiconductor crystal forming the semiconductorelement 1 is not restricted to the p-type. The n-type is alsoacceptable, in which case a p-type diffusion layer is formed.

3) The diffusion layer 3 and the pn junction 4 can also be formed byusing another semiconductor thin-film deposition method such as ChemicalVapor Deposition.

4) The antireflection film 7 may be constituted by another insulatingfilm such as a titanium oxide film or a silicon nitride film, in placeof a silicon oxide film.

5) Either one or both of the electrodes 6 a and 6 b can be formed byusing any electrode material such as gold, silver, copper, aluminum,antimony, an alloy of antimony and gold, gallium, an alloy of galliumand silver, and an alloy of gallium and gold, and by using a paste ofsuch material.

6) In place of the light transmitting member of the semiconductor module20 and 20A, a structure, which is formed by mounting reinforced glassplates on both sides of the semiconductor module, causing a transparentEthylene Vinyl Acetate (EVA) resin or the like to fill the area betweenthe reinforced glass plates, and then sealing the ends by means of aframe, could also be adopted.

7) The quantity, disposition, and form of the semiconductor devicesmounted in the semiconductor module 20, 20A, 40, are not restricted tothose of the above embodiments and can be set freely. For example, it isalso possible to obtain a semiconductor module with a flexible,sheet-like structure by mounting a multiplicity of semiconductor devicesin multiple rows and multiple columns on a thin sheet made of atransparent synthetic resin (with a thickness of 0.3 mm, for example),by connecting the multiplicity of semiconductor devices of each columnin series and the semiconductor devices in each row in parallel by meansof a conductive connection mechanism, and then molding a lighttransmitting member film on both sides of the sheet. Further, so toowith the sheet-like semiconductor module, the semiconductor devices 10can also be disposed in a plurality of layers.

8) The semiconductor module has been described by taking the example ofa semiconductor module with a light receiving function. However, thesemiconductor module of the present invention can also be applied in thesame manner to a semiconductor module with a light emitting function.However, in this case, a semiconductor device with a light emittingfunction (a spherical semiconductor device, cylindrical semiconductordevice, or granular semiconductor device) must be applied as thesemiconductor device.

A variety of spherical light emitting diodes proposed by the inventorsof the present invention in patent publications WO98/15983 andWO99/10935, and so forth, for example, can be applied as such asemiconductor device with a light emitting function. Light emittingdiodes with other types of structure could also be adopted. Such asemiconductor module with a light emitting function can be applied to aplanar light-emission type lighting device, a monochrome or colordisplay, or various display devices, and so forth.

9) Moreover, the person skilled in the art is capable of implementingother embodiments made by applying a variety of modifications to theabove embodiments without departing from the spirit of the presentinvention. The present invention is therefore not restricted to thevariety of embodiments disclosed in the above embodiments.

1. A semiconductor device, comprising: a semiconductor element, whichhas a flat surface formed by removing an apex part of a substantiallyspherical semiconductor crystal made of a p-type or n-typesemiconductor; a diffusion layer or semiconductor thin-film depositionlayer formed on a surface of the semiconductor element excluding theflat surface, and a substantially spherical pn junction formed via thediffusion layer or semiconductor thin-film deposition layer; and firstand second electrodes, which are provided on the flat surface and at anapex on the opposite side to the flat surface respectively so as to faceeach other with a center of the semiconductor element interposedtherebetween, and which are connected to both ends of the pn junction.2. The semiconductor device according to claim 1, wherein thesubstantially spherical semiconductor crystal is fabricated by causing asemiconductor melt to solidify with the substantially spherical shapethereof maintained by utilizing a surface tension of the semiconductormelt.
 3. The semiconductor device according to claim 1 or 2, wherein,when a protrusion exists near the surface of the semiconductor crystal,the flat surface of the semiconductor element is formed by removing theprotrusion.
 4. The semiconductor device according to claims 1 or 2,wherein a transparent insulating antireflection film is formed on thesubstantially spherical surface of the diffusion layer.
 5. Thesemiconductor device according to claims 1 or 2, wherein the p-type orn-type semiconductor constituting the semiconductor crystal is acompound semiconductor selected from gallium arsenide (GaAs), indiumphosphide (InP), gallium phosphide (GaP), gallium nitride (GaN), indiumcopper selenide (InCuSe), and silicon carbide (SiC).
 6. Thesemiconductor device according to claims 1 or 2, wherein thesemiconductor device is a light emitting device.
 7. The semiconductordevice according to claims 1 or 2, wherein the semiconductor device is asolar cell.
 8. The semiconductor device according to claims 1 or 2,wherein the semiconductor device is a photodiode.
 9. The semiconductordevice according to claims 1 or 2, wherein the semiconductor device is aphototransistor.
 10. A semiconductor device making method, comprising: afirst step of making a substantially spherical semiconductor crystalmade of a p-type or n-type semiconductor; a second step of producing asemiconductor element which has a flat surface formed by removing anapex part of the semiconductor crystal; a third step of forming adiffusion layer or semiconductor thin-film deposition layer on a surfaceof the semiconductor element excluding the flat surface and forming asubstantially spherical pn junction via the diffusion layer orsemiconductor thin-film deposition layer; and a fourth step of formingfirst and second electrodes, which are connected to both ends of the pnjunction on the flat surface and at the apex on the opposite side to theflat surface respectively so as to face each other with a center of thesemiconductor element interposed therebetween.
 11. The semiconductordevice fabrication method according to claim 10, wherein: in the thirdstep, an insulating antireflection film is formed on the substantiallyspherical surface of the diffusion layer when the pn junction is formed;and, in the fourth step, electrode materials are provided on the flatsurface and at the apex on the opposite side to the flat surfacerespectively so as to face each other with the center of thesemiconductor element interposed therebetween, and first and secondelectrodes are formed from this pair of electrode materials.